The present invention relates to a plasma processing apparatus in which plasma is generated to process a surface of a substrate to be processed under low pressure (reduced pressure) atmosphere.
In a field of mounting techniques, high-density mounting is required as electronic equipment is made smaller and has higher functions. Therefore, connection of a device or element to a mounting substrate is made fine, and hence mounting with higher reliability is required. One method for ensuring reliability is a method of modification of a property of a surface with plasma. For example, since organic contaminants attached to the surface are removed by this plasma processing, bonding strength of wire bonding, wettability, and adhesion between the substrate and a sealing resin can be improved. That is, surface activation action, in which the substrate surface is activated by oxygen plasma, a carboxyl group (COO), carbonyl group (C═O), or the like is generated, is caused and leads to improvement of bonding strength. Furthermore, surface washing (cleaning) action occurs due to sputtering action by argon ions or oxygen ions.
In particular, when ions such as chlorine remain on the substrate surface in a flexible circuit board constituted by a film or the like, a circuit may corrode due to moisture surrounding the substrate and a voltage applied between wiring lines on the substrate. Therefore, chlorine or the like attached to the surface is removed by plasma.
As a conventional constitution of such plasma processing, several films are manually placed in a chamber, and a series of operations including closing of a chamber lid, vacuum roughing, high vacuuming, gas valve opening, high frequency power application, stopping of high frequency power application, atmospheric pressure recovery, and opening of the chamber are manually performed one by one. Vacuum pressure is confirmed by using a vacuum gauge, and time of high frequency power application is measured by using a stop watch.
However, since batch processing is inevitably performed in the apparatus having the above constitution, its throughput is limited. Furthermore, since a film is manually placed and removed, the film may be contaminated. Furthermore, since a blank occurs between washing and a subsequent step, management of the film is difficult.
Accordingly, an object of the present invention is to provide a low pressure plasma processing apparatus and method with which a throughput can be improved, film contamination can be effectively prevented, and a film can be easily managed, thus solving the above issues.